PRELIMINARY CHARACTERIZATION OF A NEW EXO-BETA-(1,4)-GALACTANASE WITHTRANSFERASE-ACTIVITY

As a prerequisite to the study of the fine chemical structure of the b ranched region of pectin, an exo-beta-(1,4)-galactanase was purified f rom a commercial preparation (Pectinex AR). Purification was carried o ut by precipitation with 70% saturated ammonium sulfate, preparative e lectrofocusing, anion-exchange chromatography and affinity chromatogra phy on cross-linked alginate. Exogalactanase specific activity was 999 nkat mg(-1) and the enzyme was devoid of beta-(1,3)- or beta-(1,6)-ga lactanase, arabinanase, beta-D-galactosidase and alpha-L-arabinofurano sidade activities. Residual exopolygalacturonase activity represented 2.9% of the galactanase activity. Sodium dodecyl sulfate-polyacrylamid e gel electrophoresis and isoelectric focusing showed two close bands with molecular weights of 120 000 and 90 000 and pHi of 3.8 and 4.1, r espectively. The enzyme acted in an exo manner and its activity was op timum at pH 3.5 and 60 degrees C. When incubated with galacto-oligosac charides, new oligosaccharides with a higher degree of polymerization appeared, indicating the ability of the enzyme to transfer galactose r esidues.